Patent GB-789527-A (GB)
Title: Load-supporting arrangement
IPC: F22B37/14
Filed: 1954-01-22
Abstract: 789,527. Supporting pipes. GENERAL SPRING CORPORATION. Jan. 22, 1954 [Oct. 7, 1953], No. 1969/54. Class 99(2). [Also in Group XXXII] In a load supporting arrangement for exerting a substantially constant supporting force on a load (e.g. piping) that is movable up and down within a predetermined range of movement a lever system including a load supporting arm is mounted for rotation about a pivot on a frame, there being provided spring means anchored to the frame and connected to the lever system to produce a turning moment of the lever system about the pivot, the load being supported from the load-supporting arm by a linkage connected at one end to the load and at the other end to the load-supporting arm and exerting a pull in an angular direction about the pivot so as to oppose the moment produced by said spring means, said lever system being rotatable about the pivot with the load-supporting arm movable along an arcuate path from an upper position through a horizontal position to a lower position, whereby the moment exerted by the load on the lever system is a sine-like curve as a function of the angle of the load-supporting arm and has a maximum, the curve being modified according to the horizontal displacement of the point of connection of the linkage to the load relative to the point of connection of the linkage to the load-supporting arm, and the turning moment produced by the spring means as said lever system moves is also a sine-like curve having a maximum, and in which the angular position about the pivot of the connection between the linkage and the load supporting arm is so arranged relative to the angular position about the pivot of the connection between the spring means and the lever system that the phases of the two moment curves are substantially coincident, whereby substantially to compensate for the " arcing factor " (as herein defined) and/or the radius and amplitude of the horizontal travel of the load relative to the connection between the linkage and the load supporting arm. It has been found that sizeable deviations in the actual support force can occur in typical spring supports because of (a) arcuate travel of the support-arm load pivot, herein called the " arcing factor," (b) distance between the pivot connection to the supported object and the support-arm load pivot, i.e., load rod length, and (c) horizontal movement of this pivot connection relative to the support-arm load pivot. These latter two factors may also be considered as a function of the radius and amplitude of horizontal movement of the point of connection to the load relative to the supportarm load pivot. It has also been found that in spring supports a type of phase shift is produced between the moment curve of the spring force and the curve of the actual effective load moment arm, causing the vertical component of the load supporting force to be too large over a portion of the travel of the support arm and too small over the remainder of the travel. By adjusting or appropriately selecting, the angular relationship between the supporting arm and the spring lever, these two curves are brought more nearly into coincidence over a large and favourable portion of each curve, and an additional correction force may then be provided over the remainder of the curves to provide a much more nearly constant support action than in prior spring support hangers. In certain instances the supports can be adjusted so that the arcing factor effect compensates for the horizontal travel of the load. Adjacent pairs of spring supports can be arranged to face in opposite directions so that any slight residual horizontal components cancel out. Adjustability of the supporting devices and their standardization to utilise different sizes of springs enables a single size of support to accommodate a wide range of loads and of movements both vertical and horizontal. Figs. 7, 8, 10b and 11 show one embodiment. The weight of the pipe load 20 pulls down on the support arm pivot 29 causing the arm 30 to tend to rotate in a counterclockwise direction about the main pivot 31. In order to oppose this counterclockwise movement of the load a clockwise couple is produced by lower and upper compression springs 36. A booster spring 45 is usually adjusted to begin acting when the arm swings below approximately its mid range or horizontal position such as is shown in Fig. 7. The booster spring advantageously is very small relative to the main springs 36 its purpose being to aid in correcting the deviation in load supporting force caused by departure of the load rod 28 from a true vertical line of support but if desired a part of the load supporting function can be taken over by the booster as in U. S. A. Specification 2,145,704 The pivot 29 extends through a horizontal hole in an adjustable block 52 fitted freely between the sides of the supporting arm 30. When the position of pivot 29 can be accurately determined the adjustment block 52 and associated parts may be omitted. The effective length of tension rods 38 may be adjusted by nuts 72. If instead of positioning the hanger with pivot 29 vertically above pivot 26 when the arm 30 is horizontal it is positioned beneath the position of the pivot 29 when one quarter way up or down from the limits of operation the deviation of the supporting force will be one half to the right and one half to the left. This expedient is sufficient for small deviations. In another case assume that the pipe clamp pivot 26 with the pipes cold hangs at a given position and that as the pipes come up to operating temperature the pivot 26 rises an amount within the range of the device and moves to the right at a distance equal to about ¢ this vertical travel. The support is arranged so that when the piping is heated to bring the clamp pivot 26 to mid-height the pivot 29 is in mid position directly above the clamp pivot 26. As the pipe cools down the pivot 26 moves down and towards the left while at the same time the pivot 29 moves in the opposite direction because of its arcuate path. The result is to produce an arcing factor effect which is about twice that of a purely vertically moving load. As the pipes warm up from mid temperature pivots 26 and 29 move up and to the right. Thus above mid-position the load acts more or less as a freely hanging load and produce a true sine moment. The effective length of spring levers 42 can be adjusted simultaneously or individually. A scale 95 and pointers 96 indicate the adjusted position. The adjustment is made by rotating a pair of discs 98 to screw eye bolts 100 out or in along the length of the levers 42 thus moving the spring pivot shafts 43 respectively toward or away from the ends of levers 42. Pointers 96 project from the inner ends of bolts 100 out through slot 116 in block 110 and over scale 95. The adjustment disks 98 may be individually turned to compensate for a stiffer spring so as to produce a substantially pure couple about pivot 31. Thereafter the adjusting disks 98 may be turned simultaneously by means of a two-pronged fork a spanner with prongs spaced to fit into pairs of holes 118 in the edges of the discs. In another embodiment, Figs. 1-5, a combined capacity and travel indicator scale 120 is connected to an extending end portion of the upper pivot 43 and arranged to be read against an arc 122 and graduations 123 scribed on the outer face of one frame member 33 and concentric with main pivot 31. The position of the load, i.e., " High " " Mid " or " Low " is determined by comparing the scale with the graduations and three radial lines 126. In Fig. 1, the load is in top position with the upper lever 42 stopped against one of the three angle braces 127 to which support rods 35 are attached. In Fig. 3, the load is at mid position. It is possible to omit one of the springs on each side or to use lighter springs on each side or it is possible to use only one or both springs acting on one lever and to omit the lever and spring assembly on the other side of the main pivot. The adjustment of the capacity is made by a hexagonal turnbuckle sleeve 130 which receives the inner ends of both spring pivot adjusting eye bolts 100 whose eyes are straddled on shafts 42. A pair of forks 164 project out and down from the supporting arm cross member 150 with their bifurcated ends spaced to straddle the booster spring adjustment bolts 158, Fig. 5, and engage square nuts 166 thereon backed up by hexagonal lock nuts. As seen in Fig. 1 with the supporting arm 30 in the high position forks 164 are clear of bolts 158. As seen in Fig. 3, the forks engage the tops of the square nuts and as the load travels down toward low position booster spring 45 is stretched. In the extreme low position arm 30 is stopped by the locknuts engaging tongues 160. To indicate the position at which the booster spring comes into action a pair of scales 170 project down from the ends of booster cross piece 156, Figs. 3 and 5. When adjusted to an increased capacity, say 8 per cent, the square nuts are turned up until their top surfaces are aligned with an 8 mark or the scales so that the booster spring comes into action just a little before mid-position and viceversa when adjusted for less than rated capacity. The reading on scales 170 in general should be made to agree with the reading on scale 120. A third embodiment is shown in Figs. 12 and 14. The overall length of this support is greatly reduced by use of tension springs 36 mounted to extend through the spring lever arms 42 into trunnion mounted spring sockets 39. The lever system is of welded construction. Across the free end of the supporting arm near the pivot 29 is welded a spacer 176, The spring levers 42 are formed by two spaced bars 138 one of which is welded at an angle across the inside of the hub end of each of two spaced straight elements 140 forming the load arm 30. A second spacer element 178 is welded between the hub ends of the element